Center for Integrative Genomics, University of Lausanne, Switzerland

Two postdoctoral positions (2 years with possible extensions up to 5 years) are available immediately in the evolutionary genomics group of Henrik Kaessmann.

We are seeking highly qualified and enthusiastic applicants with strong skills in computational biology/bioinformatics, preferably also with experience in data mining and comparative or evolutionary genome analysis.

We have been interested in a range of topics related to the functional evolution of genomes from primates (e.g., the emergence of new genes and their functions) and other mammals (e.g., the origin and evolution of mammalian sex chromosomes). In the framework of a recently launched series of projects, a large amount of transcriptome and genome (e.g., epigenome) data are being produced by the wet lab unit of the group using next generation sequencing technologies for a unique collection of tissues from representative mammals and outgroup species (e.g., birds). Topics of current projects based on these data include the origins and/or evolution of protein-coding genes, alternative splicing, microRNAs, long noncoding RNAs, and dosage compensation.

The postdoctoral fellow will perform integrated evolutionary/bioinformatics analyses based on data produced in the lab and available genomic data. The specific project will be developed together with the candidate.

The language of the institute is English, and its members form an international group that is rapidly expanding. The institute is located in Lausanne, a beautiful city at Lake Geneva.

For more information on the group and our institute more generally, please refer to our website: http://www.unil.ch/cig/page7858_en.html

Please submit a CV, statement of research interest, and names of three references to: Henrik Kaessmann (Henrik.Kaessmann@unil.ch).

Webpage : http://www.unil.ch/cig/page7858.html

Find the detail paper at http://bib.oxfordjournals.org/content/early/2013/06/25/bib.bbt043.full

Address of the bookmark: http://bib.oxfordjournals.org/content/early/2013/06/25/bib.bbt043.full

sed ':a;N;$!ba;s/\n//g' filename.txt > newfilename_oneline.txt

To get average for a column of numbers (here the second column $2):

awk '{ sum += $2; n++ } END { if (n > 0) print sum / n; }'

To get sequence length for all sequences in a fasta file:

awk '/^>/ {if (seqlen){print seqlen}; print ;seqlen=0;next; } { seqlen = seqlen +length($0)}END{print seqlen}' \
filename.fasta

To copy (move, rename, etc) files based on their list in a text file:

cat file_list.txt | while read line; do cp "$line" complete_dataset/"$line"; done

To split bam files into sets with mapped and unmapped reads:

samtools view -F4 sample.bam > sample.mapped.sam
samtools view -f4 sample.bam > sample.unmapped.sam

To gzip all your fastq files using gnu parallel and gzip:

parallel gzip ::: *.fastq

To gzip all your fastq files using pigz:

pigz *.fastq

To count all sequences in a fasta file:

grep "^>" yourfile.fasta -c

To count all sequences in all fasta files in your current directory:

for a in *.fasta; do ls $a; grep "^>" -c $a; done

To keep only one copy of duplicated lines:

awk '!seen[$0]++'

To sum assembly size from SPAdes contigs.fasta or scaffolds.fasta file:

grep "^>" scaffolds.fasta | cut -f 4 -d '_' | paste -sd+ | bc

To remove everything after the first space at each line, e.g. to to simplify fasta headers:

cut -d' ' -f1 < your_file

To count reads in a all .fastq.gz files in your current folder (fast, using gnu parallel):

parallel "echo {} && gunzip -c {} | wc -l | awk '{d=\$1; print d/4;}'" ::: *.gz

To count reads in a all .fastq.gz files in your current folder:

zcat *.gz | echo $((`wc -l`/4))

To count reads in a all .fastq files in your current folder:

cat *.fastq | echo $((`wc -l`/4))

To count base pairs in a all .fastq.gz files in your current folder:

zcat *.fastq.gz | paste - - - - | cut -f 2 | tr -d '\n' | wc -c 

To split multifasta file into many fasta files:

awk '/^>/ {OUT=substr($0,2) ".fa"}; {print >> OUT; close(OUT)}' Input_File

To convert Illumina FASTQ 1.3 to 1.8:

sed -e '4~4y/@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghi/!"#$%&'\''()*+,-.\/0123456789:;<=>?@ABCDEFGHIJ/' f.fastq

To convert FASTQ to FASTA:

sed -n '1~4s/^@/>/p;2~4p' 

To get fastq read length distribution:

cat reads.fastq | awk '{if(NR%4==2) print length($1)}' | sort | uniq -c

To deinterleave interleaved fastq file:

cat myf.fq | paste - - - - - - - - | tee >(cut -f 1-4 | tr "\t" "\n" > myfile_1.fq) | cut -f 5-8 | \
tr "\t" "\n" > myf2.fq 

To filter and sort contig identifiers from SPAdes assembly (e.g. here lenght >= 4000 + coverage >=100):

grep "^>" scaffolds.fasta | sed s"/_/ /"g | awk '{ if ($4 >= 4000 && $6 >= 100) print $0 }' | sort -k 4 -n | \
sed s"/ /_/"g

To append something to all headers of your fasta files:

sed 's/>.*/&YOURSTRING/' filename.fasta > new_filename.fasta

To replace/squeeze multiple adjacent spaces by only one space: 

tr -s " " < file

To filter fastq based on length (here larger than or equal to 21, but smaller than or equal to 25.

cat your.fastq | paste - - - - | awk 'length($2)  >= 21 && length($2) <= 25' | sed 's/\t/\n/g' > filtered.fastq

To print difference between the last and first row in 5th column:

awk '{if (!first){first=$5;}; last=$5;} END {print last-first}' myfile.txt

To sample only 200 first bases from all sequences in a multifasta file (e.g. from assembly scaffolds.fasta file here):

awk '/^>/{ seqlen=0; print; next; } seqlen < 200 { if (seqlen + length($0) > 200) $0 = substr($0, 1, 200-seqlen);\
 seqlen += length($0); print }' scaffolds.fasta > 200bp_scaffolds.fasta

 To pipe a compressed fasta file directly into makeblastdb.

gunzip -c fasta.gz | makeblastdb -in -

To remove sequences with duplicate fasta headers from a fasta file.

awk '/^>/{f=!d[$1];d[$1]=1}f' in.fasta > out.fasta

Dated : 04 Dec 2013 - 06 Dec 2013

More at : http://www.clinicalgenomicsinformatics.com/

Many times in bioinformatics we need to deal with huge datasets which  are more than 100GB size. The traditional way to analysis a file is using the while loop

while (FILE){

Do something;

}

This is very slow(since we are using only one processor) and if we have 500 million lines in the dataset it takes more than a day to iterate through the whole dataset. So how do we make best use of all our processors and get the work done quickly?

Here is a very simple and efficient technique with perl which i have been using. I am  more inclined towards using perl fork than perl threads.

One of the oldest way to fork is

my $fork = fork();
if($fork){   
push (@childs,$fork); 
}
elseif($fork==0){
your code here;
exit(0);
}
else{die “Couldnt fork : $!”;}

## wait for the child process to finish
foreach(@childs){
my $tmp=waitid($_,0);
}

what a fork does is it creates a child process and takes the variables and code with it to analyze it separately (detached from the parent process) and thus a separate process is created( which usually runs on a separate processor). Thats it!! One big disadvantage of forking is its very difficult to share variables among the different processes. I will show you how to do it easily but still it has its own drawbacks.

Okie, now if you really do not want to use fork in your code, that’s okie too..There are many useful modules which do it for you very efficiently. One really useful module is Parallel::ForkManager. You can use Parallel::ForkManager to manage the number of forks you want to generate (number of processors you want to use).

Simple usage:
use Parallel::ForkManager;
my $max_processors=8;
my $fork= new Parallel::ForkManager($max_processors);
foreach (@dna) {
$fork->start and next; # do the fork
you code here;
$fork->finish; # do the exit in the child process
}
$pm->wait_all_children;

so you will be generating 8 forks which do the same thing for your each element of array. when one child finishes, Parallel::ForkManager generates a new one and thus you will be using all your processors to analyze the data. Now, if you have generated 8 child processes and want to write the data to one file. You need to lock the file to do this, because you will have problems with the buffering. You can lock the file using flock command.

open (my $QUAL, “myfile.txt”);
flock $QUAL, LOCK_EX or die “cant lock file $!”;
print $QUAL “$output”;
flock $QUAL, LOCK_UN or die “$!”;
close $QUAL;

I would not suggest using flock when dealing with multiple processes because it will decrease the processing efficiency( each child process must wait for the lock to be released by the other child process). Instead, I would suggest each fork writing to a separate file and after the processing just concatenating them.

Putting it all together, If you have 100GB data you can do this

step 1 : split the dataset equally according to number of processors you have. this may take a few hours(about 2-3 hrs for 100GB file)
You can use unix “split” command for this
for example:
my $number_split=int($number_of_entries_in_your_dataset/$max_processors);
my $split_Files=`split -l $number_split “your_file.fasta” “file_name”`;

step2: open you directory comtaining you split files and start Parallel::ForkManager.
For example:
opendir(DIRECTORY, $split_files_directory) or die $!; ### open the directory
my $fork= new Parallel::ForkManager($max_processors);
while (my $file = readdir(DIRECTORY)) { ### read the directory
if($file=~/^\./){next;}
print $file,”\n”;
########## Start fork ##########
my $pid= $super_fork->start and next;
Whatever you want to do with the split file ;
analyze my piece of $file;
######### end fork ###############
$super_fork->finish;
}
$super_fork->wait_all_children;

So basically each processor will be active with its piece of data (split file) and thus you have created 8 processes at one time which run without interfering with the other process. I again will not suggest writing output from each child process to one file(for reasons above). Write output from each fork to a separate file and finally concatenate them. Thats it, you have just increased your program speed by 8 times!! Isnt it easy?

Note:
You may worry about concatenation of the output each child generates, since it does take some time(remember 100GB). I think now you can use a mysql database LOAD DATA LOCAL INFILE command to load all the files into a single table(Should take about 3hrs for 100Gb dataset) and then export the whole table into one file. This should be faster than just concatenating them using “cat” command.(correct me if I am wrong)

Or much simpler way is to use pipes

cat output_dir/* | my_pipe or my_pipe <(file1) final_file;

Thats it guys!! Enjoy programming and please do comment. I am not a computer scientist so forgive me for any mistakes and if any please report them. Thank you.

Requirements
- 3-5 years of relevant bioinformatics experience such as public data mining,
processing, analysing and visualising omics data, etc.
- Ph.D., Masters or Bachelors in Bioinformatics, Biotechnology,
Computational Biology, or related field.
- Understanding of molecular biology and biochemistry.
- Comfort and experience with biological research and data.
- Proficient in a programming language used for bioinformatics such as R or
python.
- Excellent communication skills.
- Ability to summarise and simplify complex analyses for a non-technical
audience.
- Strong analytical skills, curiosity and a knack to solve difficult problems.
- Work well in multi-disciplinary teams with people of vastly different
backgrounds.
- Demonstrated success in collaboration and independent work.

More at https://angel.co/elucidata/jobs/460104-senior-bioinformatics-scientist